Under further digitalization and development of networking, audio and visual (AV) apparatuses, such as a TV and a recorder are getting connected via a digital interface. Some apparatuses even have two or more interfaces. In some cases, for example, a TV and a recorder can be connected via both an IEEE 1394 digital interface and an HDMI.
Here, the TV cannot determine whether the IEEE 1394 interface and the HDMI are connected to the same apparatus or each of the IEEE 1394 interface and the HDMI is connected to a different apparatus. Thus, this is troublesome for the user since he or she has to recognize the connection state of the apparatus before operating the TV.
Patent Reference 1 discloses a technique to solve the above problem. According to the technique, the TV issues, for example, a command to the recorder via the IEEE 1394 interface in order to start reproduction. Then, the TV observes the change of a HDMI signal to see whether or not the TV can detect a signal in response to the issued reproduction command, so that the TV determines whether or not both of the IEEE 1394 interface and the HDMI are connected to the same recorder.
Patent Reference 1: International Patent Publication No. WO 05/15901